Instability of automotive air conditioning system with a variable displacement compressor. Part 2. Numerical simulation

In order to determine the conservative stable region (CSR) proposed in part 1 of this paper, a dynamic model of the automotive air conditioning system with a variable displacement compressor and a thermal expansion valve is developed. The sensitivity analysis is done to show how uncertainties in input parameters influence the predicted results of system performance. The dynamic simulation is verified and the simulated results agree well with the experimental data. The CSR of automotive air conditioning system with a variable displacement compressor and a thermal expansion valve is simulated and analyzed when the vehicle speed or the air flow rate through the evaporator changes. The size of CSR is influenced by the direction and amplitude of external disturbance and the initial system state. The system is stable and the whole region is the CSR when the vehicle speed decreases or the air flow rate through evaporator increases, and the system sometimes is outside the CSR when the vehicle speed increases or the air flow rate through evaporator decreases suddenly. The influence of the initial state, change rate of compressor rotary speed and air temperature at the condenser inlet on the CSR when the vehicle speed increases is simulated. And the influence of the air temperature at the condenser inlet on the CSR when the air flow rate through evaporator decreases is analyzed, too. (c) 2005 Elsevier Ltd and IIR. All rights reserved.